Isolation of Lactose From Powdered Milk and Regular Milk
Kate, Elana
Introduction
Dried milk appeared during the turn of the 20th century. It is formed by extreme evaporation of milk. Most dried milk is nonfat because milk fat goes rancid easily. Milk’s opacity is because of the microscopic fat globules and protein bundles, which deflect light rays as they pass through the milk.
Lactose is the only carbohydrate found in milk. It is a compound of glucose and galactose, which are both simple sugars. Lactose is one fifth as sweet as table sugar. Lactose provides about 40% of the calories in human milk. Lactose cannot be used or absorbed by the human body as lactose; it has to be broken down first, into sugars by an enzyme called lactase.
Caseins are four different proteins that form micelles around calcium. One casein micelle is about one ten thousandth of a millimeter across. Around pH 4.7 (which is acidic), the casein proteins bond to each other and the milk solidifies, or curdles.
The purpose of our lab was to compare the amounts of lactose in regular nonfat milk and powdered nonfat milk.
Procedure
We began by pouring 237 mL of nonfat milk into a 400-mL beaker, which we labeled mixture R. Next, we put 23 grams of powdered nonfat milk into a separate 400-mL beaker. We added enough water so the volume equaled 237 mL. We labeled this beaker mixture P, for powdered milk. Next, we heated both beakers over Bunsen burners until they reached 45°C. Once the mixtures reached this temperature, we turned off the burners and added 10 mL of 10% acetic solution to each mixture. We stirred both mixtures. At this point, each mixture separated out into a yellow/clear liquid and a white clumpy solid. We filtered both mixtures through cheesecloth and collected the filtrates in two 250-mL beakers. Mixture P contained more solid than mixture R.
We then added 2 grams of calcium carbonate powder to each mixture. We put 5 boiling stones in each mixture and then boiled the mixtures over Bunsen burners for 10 minutes. Immediately after turning off the burners, we added a pinch of decolorizing carbon to both mixtures. This caused the mixtures to turn gray. After that, we filtered both mixtures through Büchner funnels by suction filtration. Mixture P filtered faster than mixture R.
Next, we transferred the filtrates to two 250-mL beakers. We added 5 boiling stones to each mixture and boiled both until the volumes were reduced to 30 mL. We added 125 mL of ethanol and a pinch of decolorizing carbon to both mixtures. We stirred the mixtures, which caused mixture P to turn black and mixture R to turn gray. Next, we filtered both mixtures through Büchner funnels by suction filtration. The filtrates became cloudy liquids.
We allowed the filtrates to crystallize for 24 hours in separate capped Erlenmeyer flasks. The next day, we filtered each mixture by suction filtration and washed each product with a small amount of ethanol. We allowed the products to dry and then compared the yields.
Results
Based on our results, we concluded that more lactose was isolated from regular nonfat milk than from powdered nonfat milk. We isolated 3.48 grams of lactose from the powdered nonfat milk and 6.99 grams of lactose from the regular nonfat milk. The regular nonfat milk had 3.51 more grams of lactose than the powdered nonfat milk.
Conclusions
We concluded that regular nonfat milk contained significantly more lactose than powdered nonfat milk. We realized boiling stones were necessary for this experiment. The mixtures are likely to bump around when boiled if boiling stones are absent. Bumping occurs when, instead of the expected small bubbles as a solution begins to boil, a solution forms one large bubble. This bumping could jostle the beakers and cause them to fall off the ring stands and break, which would result in a loss of data and skewed yields. We initially did this lab without the stones and ended up breaking both beakers. In addition to adding boiling stones to each mixture before boiling, it is important to measure and transfer each product carefully. We had to transfer our mixtures between various beakers and flasks, which resulted in some loss of data, which could have affected our results. Also, mixture R took significantly longer to filter than mixture P did. The filter paper clogged frequently, so we had to change the filter paper multiple times. Additionally, we could have let the mixtures sit and crystallize for more than 24 hours, which could have led to a more accurate comparison. To improve this lab we could add boiling stones originally, obtain more exact measurements, find a more efficient way to filter our mixtures and allow filtrates to sit for a longer period of time. To build on our lab, researchers could compare various types of milk to see if the fat content altered the outcome.
References
Ault, Addison. Techniques and experiments for organic chemistry. Sausalito, Calif: University Science Books, 1997.
Table of Contents
Isolation of Lactose From Powdered Milk and Regular Milk
Kate, Elana
Introduction
Dried milk appeared during the turn of the 20th century. It is formed by extreme evaporation of milk. Most dried milk is nonfat because milk fat goes rancid easily. Milk’s opacity is because of the microscopic fat globules and protein bundles, which deflect light rays as they pass through the milk.
Lactose is the only carbohydrate found in milk. It is a compound of glucose and galactose, which are both simple sugars. Lactose is one fifth as sweet as table sugar. Lactose provides about 40% of the calories in human milk. Lactose cannot be used or absorbed by the human body as lactose; it has to be broken down first, into sugars by an enzyme called lactase.
Caseins are four different proteins that form micelles around calcium. One casein micelle is about one ten thousandth of a millimeter across. Around pH 4.7 (which is acidic), the casein proteins bond to each other and the milk solidifies, or curdles.
The purpose of our lab was to compare the amounts of lactose in regular nonfat milk and powdered nonfat milk.
Procedure
We began by pouring 237 mL of nonfat milk into a 400-mL beaker, which we labeled mixture R. Next, we put 23 grams of powdered nonfat milk into a separate 400-mL beaker. We added enough water so the volume equaled 237 mL. We labeled this beaker mixture P, for powdered milk. Next, we heated both beakers over Bunsen burners until they reached 45°C. Once the mixtures reached this temperature, we turned off the burners and added 10 mL of 10% acetic solution to each mixture. We stirred both mixtures. At this point, each mixture separated out into a yellow/clear liquid and a white clumpy solid. We filtered both mixtures through cheesecloth and collected the filtrates in two 250-mL beakers. Mixture P contained more solid than mixture R.
We then added 2 grams of calcium carbonate powder to each mixture. We put 5 boiling stones in each mixture and then boiled the mixtures over Bunsen burners for 10 minutes. Immediately after turning off the burners, we added a pinch of decolorizing carbon to both mixtures. This caused the mixtures to turn gray. After that, we filtered both mixtures through Büchner funnels by suction filtration. Mixture P filtered faster than mixture R.
Next, we transferred the filtrates to two 250-mL beakers. We added 5 boiling stones to each mixture and boiled both until the volumes were reduced to 30 mL. We added 125 mL of ethanol and a pinch of decolorizing carbon to both mixtures. We stirred the mixtures, which caused mixture P to turn black and mixture R to turn gray. Next, we filtered both mixtures through Büchner funnels by suction filtration. The filtrates became cloudy liquids.
We allowed the filtrates to crystallize for 24 hours in separate capped Erlenmeyer flasks. The next day, we filtered each mixture by suction filtration and washed each product with a small amount of ethanol. We allowed the products to dry and then compared the yields.
Results
Based on our results, we concluded that more lactose was isolated from regular nonfat milk than from powdered nonfat milk. We isolated 3.48 grams of lactose from the powdered nonfat milk and 6.99 grams of lactose from the regular nonfat milk. The regular nonfat milk had 3.51 more grams of lactose than the powdered nonfat milk.
Conclusions
We concluded that regular nonfat milk contained significantly more lactose than powdered nonfat milk. We realized boiling stones were necessary for this experiment. The mixtures are likely to bump around when boiled if boiling stones are absent. Bumping occurs when, instead of the expected small bubbles as a solution begins to boil, a solution forms one large bubble. This bumping could jostle the beakers and cause them to fall off the ring stands and break, which would result in a loss of data and skewed yields. We initially did this lab without the stones and ended up breaking both beakers. In addition to adding boiling stones to each mixture before boiling, it is important to measure and transfer each product carefully. We had to transfer our mixtures between various beakers and flasks, which resulted in some loss of data, which could have affected our results. Also, mixture R took significantly longer to filter than mixture P did. The filter paper clogged frequently, so we had to change the filter paper multiple times. Additionally, we could have let the mixtures sit and crystallize for more than 24 hours, which could have led to a more accurate comparison. To improve this lab we could add boiling stones originally, obtain more exact measurements, find a more efficient way to filter our mixtures and allow filtrates to sit for a longer period of time. To build on our lab, researchers could compare various types of milk to see if the fat content altered the outcome.
References
Ault, Addison. Techniques and experiments for organic chemistry. Sausalito, Calif: University Science Books, 1997.
Lactose.com: The knowledge database about lactose. 2008. Friesland Foods Domo. 02 June 2009
McGee, Harold. On Food and Cooking: The Science and Lore of the Kitchen. New York: Scribner, 2004.